when u get avalaibles u can phone up a couple of days b4 to see if they have anything, you can only phone up if you have 2 or maore avaliables in a row. u normaly get avaliables following a standby, on average u may get 4 or 5 a month. when u phone up sometimes they have nothing some times only there and backs. it also depends who u get on the phone, some of the schedulers are less than helpful.
an early report payment is about £8 u get it when u report before 7am.
you u will taught all this in training so dont worry to much about it now.